Hydraulic press and protective insert therefor



Oct. 13, 1970 J, HUREK E TAL `3,533,256

HYDRAULIC PRESS AND PROTECTIVE INSERT THEREFOR Filed Jan. 2l, 1969 6223 2 fy. i

fr n Y@ A l I 7,5/ www United States Patent O 3,533,256 HYDRAULIC PRESS AND PROTECTIVE INSERT THEREFOR Jaroslav Hurek, Prague, and Jan Janek, Nachod, Czechoslovakia, assignors to Ustav pro vyzkum motorovych vozidel, Prague, Czechoslovakia Filed Jan. 21, 1969, Ser. No. 792,692 Int. Cl. B21d 22/12 U.S. Cl. 72-63 5 Claims ABSTRACT OF THE DISCLOSURE A protective insert is used in hydraulic presses between a flexible wall of a pressurized chamber and a punch during shaping of a sheet metal workpiece so that the protective insert protects the wall of the pressurized chamber. The insert includes an outer relatively hard annular member to clamp a periphery of the metal workpiece against a thrust ring to form a ange from the periphery of the workpiece. Said outer relatively hard member or component of the protective insert engages an inner yieldable plastic component of the protective insert, which directly coacts with the punch during the shaping of the sheet metal into a configuration determined by the punch, the punch extending through the harder outer member to have the sheet metal workpiece shaped directly against the punch with the pressure exerted on the workpiece from the pressurized chamber through the yieldable plastic component of the protective insert.

BACKGROUND OF THE INVENTION The present invention relates to hydraulic presses.

In particular, the invention relates to hydraulic presses which are adapted to shape articles from sheet metal workpieces.

Hydraulic presses of this general type are provided with pressurized chambers defined by a flexible wall which may be elastic and is lilled with a liquid medium. A punch pushes the sheet metal workpiece toward the pressurized chamber so that the latter becomes deformed and shapes itself around the punch while shaping the sheet metal to the configuration of the punch. In order to protect the wall of the pressurized chamber it is conventional to locate a protective insert between the wall of the pressurized chamber and the punch so that it is this protective insert which will directly engage the sheet metal workpiece. The present invention relates particularly to such a protective insert.

As the rigid punch of the press pushes inwardly toward the interior of the pressurized chamber so that the elastic wall thereof shapes itself around the punch, the protective insert situated between the wall of the chamber and the punch transmits the pressure to the workpiece and itself becomes shaped around the punch so that in effect it functions as a wall of the pressurized chamber.

Such a protective insert is required to perform two distinct tasks which, to a very large extent, are incompatible with each other. On the one hand, the protective insert is required to clamp the peripheral portion of the sheet metal workpiece against a thrust ring through which the punch extends so as to form in this way a flange in the finished article. While thus holding the peripheral portion of the metal sheet against the thrust ring, the remainder of the metal sheet, which is surrounded by its periphery, is required to yield during the advance of the punch to be shaped around the latter, so that the resulting article made from the sheet metal workpiece will have a hollow interior and will be provided at its edge with an outwardly directed ange.

ICC

These two operations, namely, holding the periphery of the workpiece, and freeing the regions surrounded by the periphery for the shaping by the punch, are substantially incompatible in that to achieve the best possible action it is necessary for the protective insert to have a high degree of hardness and substantiallly no yieldability at the region which clamps the periphery of the workpiece against the thrust ring, while at the same time the protective insert is required to be easily yieldable and elastic to adapt itself to the shape of the punch while holding the sheet metal thereagainst during the movement of the punch along its working stroke. The part of the protective insert which coacts with the periphery of the workpiece to form a flange from the latter is required to be relatively rigid, while another part of the protective insert is required to be elastically yieldable so as to be deformable to the configuration of the punch. The quality of the resulting pressed articles made from sheet metal workpieces will be greatly influenced by the operation of the protective insert, particularly at its part which clamps the periphery of the workpiece against the thrust ring. This part of the protective insert is required to perform the functions of a conventional die clamp.

It has been found in practice that with presses of the above type, having such pressurized chambers, before long there are noticeable initial traces of waviness in the sheet metal workpiece at the junction between its flat ange and the cylindrically shaped part thereof projecting from this flange and engaged by the punch during shaping. These undulatory portions progressively extend from the circumference to the center of the sheet metal workpiece, and during continued operations these undulations rapidly increase and become greater and result in unavoidable damage to the surfaces of the protective insert which, as a result, completely breaks down in a relatively short time. Therefore, it becomes necessary to frequently replace protective inserts conventionally used 'with hydraulic presses of the above referred to type. The result is that the cost of the finished articles is undesirably increased and the rate of productivity is undesirably decreased.

SUMMARY OF THE INVENTION It is accordingly the primary object of the present invention to provide a protective insert which will avoid the above indicated drawbacks.

More particularly, it is an object of this invention to provide a protective insert which on the one hand will be capable of operating effectively as a clamp for holding the periphery of a sheet metal workpiece against a thrust ring of the press, and which on the other hand will be capable of easily yielding elastically to properly shape sheet metal against a punch.

In addition, it is an object of the invention to provide a protective insert which will have a long operating life that is far longer than has heretofore been possible, with a corresponding reduction in the manufacturing costs while at the same time enhancing the quality of the articles produced, particularly articles manufactured from thin metal sheets.

Another object of the invention is to provide a protective insert which is capable of increasing the productivity while decreasing the extent to which defective articles which must be rejected. In this way there is also a reduction in the manufacturing costs.

In accordance with the invention, the protective insert has an outer relatively hard annular member or component formed with an opening into which the punch of a press is adapted to extend. This outer component is adapted to clamp a periphery of the workpiece against a thrust ring through which the punch of the press extends. The protective insert includes, in addition to this outer relatively hard component, an inner flexible elastic component which directly engages the wall of the pressurized chamber to protect this wall, and which additionally is accessible to the punch through the opening of the outer component to shape a sheet metal workpiece very precisely against the exterior surface of the punch during the advancing stroke of the latter.

BRIEF DESCRIPTION OF THE DRAWING The invention is illustrated by way of example in the accompanying drawing which forms part of this application and in which:

FIG. l is a schematic fragmentary part of the sectional elevation of that part of a hydraulic press which is provided with the structure of the invention;

FIG. 2 is a longitudinal sectional elevation of one cornponent of a protective insert according to the invention;

FIG. 3 is a longitudinal sectional elevation of another component of the protective insert of the invention;

FIG. `4 is a longitudinal sectional elevation of a further embodiment of the component shown in FIG. 3;

FIG. is a sectional elevation of a thrust ring of the press; and

FIG. 6 is a sectional elevation of another embodiment of a thrust ring of the press.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to the drawing and to FIG. 1 in particular, it will be seen that the hydraulic press schematically and fragmentarily illustrated therein includes an upper hollow cylindrical part 1 adapted to receive a ram 2 which reciprocates with respect to part 1. The ram 2 is supported by a press frame 3 which in turn is controlled hydraulically through any suitable transmission gears or the like, which are not shown since they are well known and form no part of this invention. The upper press part 1 is axially shiftable with respect to the frame 3 along a plurality of pilot pins 4 which are fixed to and extend downwardly from the frame 3, and are uniformly distributed about the press part 1. The pilot pins 4 extend freely through openings 5 formed in a ange 6 of the part 1. Only one of the openings 5 and one of the pins 4 are illustrated at the upper right of FIG. 1, where the fiange 6 is also shown. The lower end of the pilot pin 4 shown is enlarged at 5 so as to limit the extent of movement of the parts 1 and 3 apart from each other.

Within the hollow interior of the cylindrical press part 1 is an elastic container 7 having a flexible elastic wall and being adapted to be filled with a pressure medium such as a suitable liquid. The container 7 defines a pressurized chamber 7 which coacts with a punch 17 in a manner described below in greater detail. The wall of the container 7 is fixedly clamped in a duid-tight manner to the bottom end face of the ram 2 by way of a clamping plate 8 and bolts 9. In order to prevent any part of the wall of the container 7 from penetrating into any gap, which remains between the exterior surface of the ram 2 and the interior surface of the cylindrical part or body 1, a spacer ring 10 can be situated against the outer peripheral region of the lower surface 2 of the ram 2.

The elastic wall of the container 7 has a lower portion directed toward the punch 17, and a protective insert generally designated 25 bears against this lower outer portion of the container wall. The protective insert 25 consists of two components 11 and 12. The component or part 11 is a lower part which is adapted to press directly against an outer peripheral region of a sheet metal workpiece that is to be shaped in the press when the ram 2 is in its lower end position. The outer component 11 of the protective insert is of an annular configuration, while the other or inner component 12 is in the form of a flexible elastic sheet of dished configuration. It is the flexible elastic sheet component 12 which directly engages the lower portion of the wall of the container 7. The protective insert 25 cornposed of the components 11 and 12 is secured in the hollow interior of the cylindrical press part 1 by way of a metallic ring 13 which engages an inwardly directed shoulder 14 in the component 11 at the lower end of the part 1. The ring 13 acts as a spacer which prevents any mass of the component 11 from penetrating into any gap existing between the shoulder 14 and a thrust ring 16 of the press, which is received in the lower interior portion of the part 1 during operation of the press.

The press has an upper stationary part 15 which carries the thrust ring 16 that is formed with an axial or central opening 16' through which the punch 17 of the press freely reciprocates. The punch is raised along its working stroke by a hydraulic power assembly acting through a suitable transmission such as gearing or the like of the press, located in the lower portion of the press and not illustrated since it is known and forms no part of the invention.

Thus, the shaping punch 17 is also adapted to extend freely through central openign 11' in the annular outer component 11 of the protective insert, which opening 11 has a diameter that is sufficiently greater than the largest cross sectional dimension of the punch 17 to assure movement of the latter with substantial clearance through the opening 11 of the annular outer component 11 of the protective insert. As a result of this arrangement, a sheet metal workpiece 18 will not be shaped against the punch 17 by the component 11 of the protective insert 25, but exclusively through the action of the component 12 of the protective insert. The outer component 11, however, presses, due to the hydraulic pressure prevailing in the interior of the container 7, a peripheral portion of the sheet metal workpiece 18 against the thrust ring 16 so as to clamp such peripheral portion against the thrust ring 16 and to form from the workpiece an outwardly directed flange in a manner clearly shown in FIG. 1.

In order that it may function in the best possible manner, the outer component 11 of the protective insert is relatively hard and is made up of a plastic mass which, while having some degree of iiexibility, has nevertheless a hardness index which is as high as possilbe. On the other hand, the component 12 which is softer, far more elastic, and resiliently yieldable, participates directly in the shaping of the sheet meatl workpiece 18 against the punch 17 so that in effect it is only the component 12 which forms the equivalent of a female die coacting with the punch 17 and being resiliently yieldable to assure precise shaping of the sheet metal workpiece against the exterior surface of the punch.

The outer component 11 has a configuration which is clearly apparent from FIG. 3, while the inner component 12 has a configuration that is clearly seen in FIG. 2. The two components are placed directly against each other so that the outer surface of the component 12 engages the inner surface of the component 11, and the inner surface of the component 12 directly engages the wall of the container 7. The outer peripheral face of the component 11 is formed with the annular shoulder 14 for receiving the spacer ring 13. It will be noted that the inner peripheral edge of the component 11 which forms the openign 11 through which the punch 17 extends is tapered so that it will coact effectively with the softer elastic component 12 during the shaping of the workpiece 18, as indicated in FIG. l.

According to another embodiment of the invention (see FIG. 4), the outer component 11a of a protective insert is provided in its interior with a fiat metallic reinforcement 19 of annular configuration, arranged adjacent to the outer exterior surface 20 of the component 11a. This reinforcing ring-shaped sheet 19 is formed with a plurality of apertures 21 passing therethrough. During molding of the component 11a, the reinforcing ring 19 is positioned within the mold not only to assume the desired position within the component 11a, as indicated in FIG. 4, but also to enable the material of the component 11m to ow freely through the apertures 21 so that in this way the component 11a has portions filling the apertures 21 to very securely connect the ring 19 to the component 11a in the interior thereof. With this embodiment, the component 11a will be reinforced by the metal reinforcement ring 19 to further enhance the operation of the protective insert of the invention.

As shown in FIG. 5, the thrust ring 1-6 which is carried by the upper part 15 of the hydraulic press is in the form of an al1-metal annular plate formed with the axial opening through which the punch 17 passes.

According to the embodiment shown in FIG. 6, a thrust ring 16a is formed at its upper surface with an annular recess 23 which extends all the way to the inner periphery of the thrust ring and receives in its interior a plate 24 of a plastic mass or rubber having a high hardness index. The relatively hard plastic plate 24 will coact with the component 11 or 11a to very efficiently clamp the periphery of the workpiece 18 to form at this periphery the flange surrounding the drawn cupped part of the workpiece. The recess 23 is shown to stop short of the outer periphery of the thrust ring 16.

With the protective insert of the invention as described, having two individual components which are not connected to each other but simply bear against each other, perfectly pressed workpieces are achieved even if the workpieces are made of extremely thin metallic sheets. The quality of the plastic materials used for the components 11 and 12 of the protective insert of the invention will always be selected in accordance with the operations to which the protective insert are to be subjected. The outer component 11 made from a very hard plastic mass provides an extremely rigid and substantially non-resilient holding of the peripheral edge of the workpiece during the shaping thereof by the punch. The effectiveness with which the periphery of the workpiece is held approaches that which can be obtained by using mechanical die clamps or cushions of conventional pressing tools.

The softer yieldably elastic material used for the inner component 12 of the protective insert guarantees proper shaping of the work sheet 18 to the configuration of the exterior surface of the punch 17 during the advancing of the latter upwardly along its working stroke, while at the same time preventing any excessive stresses in the material of the component 12 so that component 12 will have a long operating life with the capability of a large number of workpieces being shaped with the protective insert of the invention before this insert must be changed to another insert.

The quality of the articles achieved according to the invention are greatly enhanced. At the same time, manufacturing costs are reduced, the results being far in advance of those which can be achieved in cases where a protective insert of a single plastic material is used. Such single plastic material can only be a compromise between the conflicting requirements of the operations to which different parts of such a plastic material must be subjected.

We claim:

1. For use in a hydraulic press having a liquid-fluid pressurized chamber defined by a flexible wall, and in cluding a punch around which said flexible wall distributes itself during shaping of a sheet metal workpiece around said punch, while the latter extends through a thrust plate against which a flange portion of the sheet metal workpiece is adapted to be retained during the shaping of the sheet metal workpiece, a protective insert to be situated between said wall of said pressurized chamber and said punch, said insert including an outer annular component formed with a central opening through which said punch can extend, and being situated directly next to Said thrust ring for clamping a peripheral portion of the workpiece thereagainst to form said flange portion, said outer annular component having a relatively high degree of hardness, said insert further including an inner exible elastic sheet component situated between said outer component and the wall of the pressurized chamber, Vwith a central region of the inner component accessible through said central opening in the outer component, so that said inner flexible elastic sheet component coacts with the workpiece to shape the latter at its portion which surrounds said punch, while said flange portion of the workpiece is retained against said thrust plate by said outer component of the protective insert.

2. The combination of claim 1 and wherein said outer component has a diameter, at said. central opening, larger than the cross section of said punch so that the latter can move with clearance through said outer component.

3. The combination of claim 1 and wherein said outer component has a metallic annular reinforcement sheet imbedded therein adjacent to an exterior surface of said outer component, which is directed away from said inner component but is directed toward said thrust ring.

4. The combination of claim 3 and wherein said metallic reinforcement is formed with apertures passing therethrough and through which material of said outer component extends.

S. The combination of claim 1 and wherein said thrust ring is formed with an upper recess, and an annular ring of a plastic material of relatively high hardness is received in said recess and coacts with said outer component to clamp the outer peripheral portion of the sheet metal workpiece therebetween.

References Cited UNITED STATES PATENTS 3,264,854 8/ 1966 Carlisle 72-63 3,287,950 ll/ 1966 GrankOwSki 72-63 3,334,504 8/1967 Mller 72--63 RICHARD I. HERBST, Primary Examiner 

